Carbon stocks and flows in forest ecosystems based on forest inventory data

Abstract

Countries are currently reporting changes in carbon pools of forests to UNFCCC. According to the reporting guidelines methods should be transparent and verifi able, and also the quantifi cation of the uncertainty is asked. The objective of the thesis was to develop methods for quantifying carbon stocks and fl uxes at national scale based on forest inventory data. To estimate tree biomass of forests, representative BEFs (biomass expansion factors) with uncertainty estimate were developed for Finland. A method for quantifying carbon fl ux of branches to soil was also developed. Both biomass and branch litterfall estimates were tested against independent measurements. Biomass estimation method and litterfall estimates were applied with Finnish forest inventory data to estimate carbon stocks and their changes for Finnish forests for 1922-2004. In this application main sources of litter were quantifi ed based on forest inventory data and fed into dynamic soil decomposition model in order to estimate soil carbon stocks and its changes. Application of BEFs, litterfall estimates and soil model gave time series of carbon stocks in Finnish forests. Results showed that tree carbon stock of Finland increased from 510 Tg to 780 Tg, while carbon in mineral soils increased from 850 Tg to 960 Tg during 80 year period. It was also found that there were high inter annual variation with soiland tree carbon stocks caused by harvestings and temperature. According to the results, the NPP (net primary production) of Finnish forests has increased from 0.3 to 0.4 kg m during studied period, while NBP (net biome production) was positive since 1970s. Results emphasize the importance of complete counting of changes of forest carbon pools i.e., trees, litter, soil and dead wood. Completeness will be important especially if forest management is used as a tool to mitigate climate change by enhancing carbon sinks of forests.